Pfizer Inc. (NYSE: PFE) will acquire NextWave Pharmaceuticals, a privately held specialty pharmaceutical company for as much as $700 million.

The purchase price includes a $255 million payment to shareholders upon the closing of the deal, plus $425 million in possible additional payments based on sales milestones.

New York-based Pfizer, also a pharmaceutical company, had previously entered into a merger agreement with NextWave and has already made a $20 million payment.

NextWave, headquartered in Cupertino, Calif., develops Quillivant XR, an extended-release medication, and CII, a medication for attention-deficit hyperactivity disorder.

Jefferies & Co. Inc. acted as Pfizer’s financial adviser, while law firms Kaye Scholer LLP and Ropes & Gray LLP handled legal matters. Aquilo Partners LP ran the sale of NextWave, while Cooley LLP acted as legal counsel.